OK... I posted a while back about upgrading my rear suspension - I decided to start with the shocks.
Well, I went with a set of Spax adjustable rear shocks - I know people say Konis are best but locally I could pick up a set of new Spax shocks for half the price of the Konis. I just figured I would take a risk on them. I couldn't find anyone recommending NOT to use them anyway
So, immediately after changing the shocks, I started hearing a knocking noise from the rear-right when going over small bumps. On a perfectly flat road, it's fine, but as soon as I get a few bumps, it sounds exactly like the shock is rattling around.
I got back underneath the car pulled both shocks around to check for play. They're rock solid. Bouncing the suspension doesn't make any noise. I pushed the exhaust around, checked the drop links, anti-roll bar, etc, nothing.
So, I drove off again, and decided to take it over some large speed bumps to see if I could get a better idea of where the noise was coming from. I didn't go over anything too fast though, and didn't really hear anything different. I parked the car overnight and drove it to work this morning.
Now, I'm getting the same rattle from the rear-right, but also a very heavy/hard bang from the rear-left when going over bigger bumps in the road. It sounds really awful.
My two thoughts are:
1) These Spax shocks are junk!
2) The anti-roll-bar and drop links look very old and rusty. The shocks I took off looked very old as well. I'm wondering if the stiffer shocks I've put on have taken out the 'give' that was there with the older shocks, so now something else can't handle the additional forces that might be running through the suspension.
Only trouble with point 2 is I can't find any play anywhere, all the rubber bushes look fine. As for point 1, well the car is driving/handling a lot better on these shocks - they seem great!
I'm about to get back home now and have another look under the car, if anyone has any ideas of what to look at I'd appreciate it.
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well neither sway bar or shock is needed for the car to drive straight over a speed bump....so remove the sway bar entirely and see if it's still knocking.
also, check that the bolt hole size on the shock matches the bolt diameter. if the hole is too big, it'll rattle. but won't show up much when you check for play since shock is still held firm under its own gas pressure.
Make sure the SPAX shocks are for your car. I think the rear shocks are different between the early (steel rear suspension) and late (alloy suspension). I think the SPAX are designed for the early 944. Also on my 944 I had once a noise like that it turned out the lower shock bolt came loose. Also are the SPAX adjustable? If so try to play with the adjustable setting.
you mean to say that they are for a late 944 ,can you give me the part number and your supplier contact info? or better yet are you considering selling them?
I don't think they are for a late 944... I took the shocks off today and checked out the play in the bolts. The tops of the struts have the correct bolt diameter size, whereas the bushings at the bottoms are incorrect and are too big. I don't think the S2 would have a larger bolt at the bottom than the top, although I might be wrong!
I think design911 has them at the same price as well. Personally though I think the problem is a manufacturing fault, so I'll be contacting them tomorrow with what I've found.
In the meantime, today I managed to fit a metal sleeve over the bolts to pad out the gap and they fit much better now. The suspension is much better now - I've got it set to a fairly hard setting, although I did find the shocks made a loud squeaking noise when set to a particular point (about 12 clicks into it's 28-click adjustment from soft to hard), which kind of makes me think these shocks aren't exactly brilliantly designed!
The shock bolts are 12mm top and 14mm bottom I believe.
That might make sense then. My '85 944 has the same size top and bottom, seems a bit odd for Porsche to change it to just larger bolts at the bottom, but that would explain why these shocks didn't fit. Odd that they list them as pre-86 and apparently don't sell an 86-onwards version.
I did measure the bolts yesterday, stupidly I didn't note down the diameter, but 12mm sounds about right for the bolts on my car. It's a 19mm hex head.